i have a 96 ciera 3.1 and i just changed the anti freeze prestone green but now i have no heat and the temp gauge goes to hot then cold and back and forth so im sure its air in the system . there are two bleed valves one on the thermostat housing and one on the engine going to the heater core what is the proper procedure?

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i have a 96 ciera 3.1 and i just changed the anti freeze prestone green but now i have no heat and the temp gauge goes to hot then cold and back and forth so im sure its air in the system . there are two bleed valves one on the thermostat housing and one on the engine going to the heater core what is the proper procedure?

ok easy peasy,

When filling the system you need to have BOTH bleed valves open, until coolant starts flowing out of them. (car turned off) When coolant starts to flow out close the one it flows out of, then continue to fill until you cannot fill anymore coolant AND or both bleeder valves have had coolant drip and have been closed.

After filling the radiator as much as possible, top the expansion tank up to the cold line, now turn the the car on.

The manual states to run the car and keep an eye on the antifreeze level. Once you can feel the upper radiator hose getting hot(coming from the thermostat to the radiator) you should technically be bled as far as the manual is concerned.(make sure the expansion tank and radiator are at the proper levels this goes without saying)

I had a 2003 Buick and I for one know these are pains. IF you have trouble bleeding it like this, you may need to purchase a special funnel, one of those spill free funnels that hook up to the radiator cap, and run the engine until the fan kicks on then back off. But I would try the version in the manual before making in big moves.

2 things concern me here.. this is the 3.1 notorious for intake gasket leaks.. my Buick had this.. if you had this you will likely never get it bled properly.. at least was the case with my Buick.

The second thing.. you stated you filled with prestone green is this a universal type? If not does the 1996 have Dexcool as the OEM fill? If it had dexcool, and you didnt get a good flush before adding the green(I am assuming green is not universal?) your in for problems..

EDIT: One thing i should mention, make sure the heater core is all the way open, (temperature dial inside all the way in the red) with the blower off.

Ideally the vehicle should parked on slight incline or the nose raised, engine off and the radiator filled with the bleeder valves open. If done correctly air should be heard faintly hissing from the bleeders as coolant is added.

Start the engine, with the radiator cap off, bring it up to operating temp, heater on high, adding more coolant as necessary to top off the system. When the coolant begins to spill out of the radiator put the cap on but leave the bleeders open until only coolant runs out and the T-Stat is open. (Note: The bleeders can be temporarily closed while waiting got the t-stat open).

Once all the air is purged close the bleeders carefully, do not to over tighten and fill the overflow tank to the hot level, (no big deal if overfilled slightly).

Feel your top hose and see if it squishes liquid or air. If it has air in it, take it off its radiator nipple-- coolant won't fall out, though it should.

Lift the hose up so it's the high spot, stick a funnel in, and "backfill" the engine through this hose until it starts dripping out the radiator nipple. Quickly stick the hose back on, tighten the clamp, then do the jig with warming it up and the bleeder nipples.

The premise of this operation is sometimes you get a "tight" water pump or thermostat that won't leak enough water internally to fill the motor.... or won't leak enough air to let water come in behind it to fill it up.

For all those who say to open the heater core up, it really doesn't matter on GM stuff. Their cores run hot all the time- no heater control valve. In fact, most Fords from at least the 90's on and most Chryslers too.

EDIT: It is a good idea to do it anyway, as it's a good indicator of whether or not there is flow through the heater core and not an air lock.